WASHINGTON -- The famous Crab Nebula supernova remnant has erupted in an enormous flare five times more powerful than any flare previously
seen from the object. On April 12, NASA's Fermi Gamma-ray Space
Telescope first detected the outburst, which lasted six days.

The nebula is the wreckage of an exploded star that emitted light
which reached Earth in the year 1054. It is located 6,500 light-years
away in the constellation Taurus. At the heart of an expanding gas
cloud lies what is left of the original star's core, a superdense
neutron star that spins 30 times a second. With each rotation, the
star swings intense beams of radiation toward Earth, creating the
pulsed emission characteristic of spinning neutron stars (also known
as pulsars).

Apart from these pulses, astrophysicists believed the Crab Nebula was
a virtually constant source of high-energy radiation. But in January,
scientists associated with several orbiting observatories, including
NASA's Fermi, Swift and Rossi X-ray Timing Explorer, reported
long-term brightness changes at X-ray energies.

"The Crab Nebula hosts high-energy variability that we're only now
fully appreciating," said Rolf Buehler, a member of the Fermi Large
Area Telescope (LAT) team at the Kavli Institute for Particle
Astrophysics and Cosmology, a facility jointly located at the
Department of Energy's SLAC National Accelerator Laboratory and
Stanford University.

Since 2009, Fermi and the Italian Space Agency's AGILE satellite have
detected several short-lived gamma-ray flares at energies greater
than 100 million electron volts (eV) -- hundreds of times higher than
the nebula's observed X-ray variations. For comparison, visible light
has energies between 2 and 3 eV.

On April 12, Fermi's LAT, and later AGILE, detected a flare that grew
about 30 times more energetic than the nebula's normal gamma-ray
output and about five times more powerful than previous outbursts. On
April 16, an even brighter flare erupted, but within a couple of
days, the unusual activity completely faded out.

"These superflares are the most intense outbursts we've seen to date,
and they are all extremely puzzling events," said Alice Harding at
NASA's Goddard Space Flight Center in Greenbelt, Md. "We think they
are caused by sudden rearrangements of the magnetic field not far
from the neutron star, but exactly where that's happening remains a
mystery."

The Crab's high-energy emissions are thought to be the result of
physical processes that tap into the neutron star's rapid spin.
Theorists generally agree the flares must arise within about
one-third of a light-year from the neutron star, but efforts to
locate them more precisely have proven unsuccessful so far.

Since September 2010, NASA's Chandra X-ray Observatory routinely has
monitored the nebula in an effort to identify X-ray emission
associated with the outbursts. When Fermi scientists alerted
astronomers to the onset of a new flare, Martin Weisskopf and Allyn
Tennant at NASA's Marshall Space Flight Center in Huntsville, Ala.,
triggered a set of pre-planned observations using Chandra.

"Thanks to the Fermi alert, we were fortunate that our planned
observations actually occurred when the flares were brightest in
gamma rays," Weisskopf said. "Despite Chandra's excellent resolution,
we detected no obvious changes in the X-ray structures in the nebula
and surrounding the pulsar that could be clearly associated with the
flare."

Scientists think the flares occur as the intense magnetic field near
the pulsar undergoes sudden restructuring. Such changes can
accelerate particles like electrons to velocities near the speed of
light. As these high-speed electrons interact with the magnetic
field, they emit gamma rays.

To account for the observed emission, scientists say the electrons
must have energies 100 times greater than can be achieved in any
particle accelerator on Earth. This makes them the highest-energy
electrons known to be associated with any galactic source. Based on
the rise and fall of gamma rays during the April outbursts,
scientists estimate that the size of the emitting region must be
comparable in size to the solar system.

NASA's Fermi is an astrophysics and particle physics partnership
managed by NASA's Goddard Space Flight Center in Greenbelt, Md., and
developed in collaboration with the U.S. Department of Energy, with
important contributions from academic institutions and partners in
France, Germany, Italy, Japan, Sweden and the United States.

Visitor Comments (8)

What would this be classified as?

Posted by Amanda Leitenberger on Thursday, 11.1.12 @ 15:54pm

Reminds me of a famous author of the 19th Century:Mary Baker Eddy, who wrote in Science and Health-"They will no longer look up to the Stars, but down from them upon the Universe"! If one would gaze at it for awhile, even with the help of a magnifying lens, one cuold almost fell BEING THERE! Beautiful color photography: below on this super Cradled Planet Earth! If Terrorist would blow up Earth as the next great target after the Twin Towers, who in the rest of the Universe would give A-DAM about us and these Terrorists: We are not even located in a prominent Galctic area of recognition!

Posted by albert kundrat on Saturday, 07.28.12 @ 23:55pm

Very good.

Posted by narayanaswami.P.S. on Tuesday, 08.16.11 @ 03:58am

There has been a lot discovered about the Crab Nebula. I would very much like it if someone would write a very good book on the Crab telling of what occurs in it and write it for the educated layman. It could be a history of this nebula up to our present day.

Marvin L. S.

Posted by Marvin L. S. on Tuesday, 06.7.11 @ 16:53pm

Outstanding, will follow, the such later.
Thanks

Posted by Rick Moll on Wednesday, 05.18.11 @ 05:02am

It's difficult to imagine what is a body of "nothing but neutrons" spinning 1800rpm, held together only by gravity. Now, if only I knew what gravity and neutrons really are.

To watch time-lapse movies of a celestial object such as the Crab Nebula is mind blowing when you think of the scale you are looking at.
Astronomy, the Universe never get boring or mundane. They grab you by the shoulders and demand that you witness their splendor.
A thought comes to mind of a famous saying by a certain Vulcan science officer when viewing the wonders of the Universe "Fascinating".

Posted by JD on Wednesday, 05.11.11 @ 17:26pm

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